Sodium alginate/poly(vinyl alcohol) alloy membranes for the pervaporation, vapour permeation and vapour permeation with temperature difference separation of dimethylformamide/water mixtures: A comparative study

In this study, sodium alginate (NaAlg)/poly(vinyl alcohol) (PVA) membranes were prepared for the separation of dimethylformamide (DMF)/water mixtures. The two polymer components were independently crosslinked chemically with glutaraldehyde. The crosslinked membranes were characterized by fourier transform infrared spectrometry (FTIR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). The permeation and separation characteristics of water/DMF mixtures were investigated using the vacuum processes pervaporation (PV), vapour permeation (VP) and vapour permeation with temperature difference (TDVP) methods. The effects of NaAlg/PVA ratio, membrane thickness, operating temperature and temperature of the membrane surroundings, feed concentration on the transmembrane permeation rate and separation factor were investigated. Optimum NaAlg/PVA ratio was determined as 80/20 (w/w) for the separation. The permeation rate in VP was lower than those in PV, whereas the separation factors were higher. The activation energies of permeation in PV and VP were calculated to be 5.070 and 2.229 kcal/mol, respectively, for a 20 wt% of DMF solution.